1. Field of the Invention
The present invention relates to an implantable lead, such as for example a pacemaker lead.
2. Description of the Prior Art
In order to make sure that a lead stays in place, for example endocardially, it is provided with a helical fixation element, which is arranged at the distal end of the lead. The fixation element can be screwed into the body tissue.
One prior art example of such a lead is disclosed in U.S. Pat. No. 4,972,848. The lead has an insulative body and a conductor extending within the insulative lead body. An electrode assembly is mounted at the distal end cavity. The conductor extends into the cavity from a proximal end thereof. A helical fixation element is electrically and mechanically attached the distal end of the conductor and is extendable out of the cavity by rotating it by means of rotating the conductor. In order for the fixation element to move forward when it is being rotated it rotates around a fixed electrode guide, which is attached to the inner walls of the cavity. The radial portions connecting the centre portion with a surrounding cylindrical portion, which is fixed to the inner wall of the cavity. The turns of the fixing element extends around the centre portion and abut on the radial portions, which advance the fixation element when it is being rotated.